Imaginary Gifts in the V Series can be akin to a morale boost as those units with their Imaginary Gifts are typically considered the leaders of their respective clans. Taken a step further:
Accel empowers reserve units allowing them to get on the field without worrying about formation.
Force empowers existing units and that encouragement allows them to fight harder.
Protect empowers backup units, giving them the power to fully guard their Vanguard.
Ibuki can be seen as every player that complains about how the game is Ruined FOREVER and loudly declares they're quitting but continues to play anyway.
Clan changes of Team Nippon:
Shin's clan in G was Murakumo but in the reboot, he is set to use Genesis which may seem strange but said clan was used by his relative Misaki in the previous two series. Also, Genesis has access to the Force imaginary gift like Royal Paladin and Gear Chronicle, the clans used by the other protagonists of the franchise.
Additionally, with Rive playing Nova Grappler instead of Tachikaze, Shin and his friends now use two clans from the United Sanctuary, one from the Dragon Empire and one from Star Gate. Just like Team Q4.
Another reason for Rive's clan change to Nova Grappler could also be a nod to how his son, Chrono, once used a Nova Grappler deck from Kamui in the G manga, Stride Generation, to test if other decks work out for him.
Also of their clans now have a Japanese theme. Shinemon's Genesis Clan represents the spiritual aspects, Mark's clan Nubatama represents ninja's and Rive's clan now represents martial arts which are all things that commonly come to mind when it comes to Japanese culture which could foreshadow their future as "Team Japan".
Tonori using Knight of Fury, Agravain as his main Grade 3 makes a lot of sense considering his character. Tonori himself gets angry if denied food for too long which happens during fights and Agravain's skill "devours" all of the rearguards into the soul as cost for its primary skill, alluding to his fighter's big appetite.
Mamoru's ace card, Dragonic Blademaster, has an ability which lets the player call a token to the field. The token mechanic in Vanguard is primarily associated with Neo Nectar, the clan Mamoru's younger sister Tokoha uses. As it is later revealed Tokoha's Ahsha can summon tokens who can mimic her power and critical.
Shinemon's phrase in the opening is that imagination is the strength of Vanguard and you can't let your opponent's imagination dominate it. So it's logical and meaningful that Esuka defeated Shinemon while also pointing out the reality of his shortcomings as self-proclaimed "manager" of Card Capital.
It's also important that when Shinemon defeats Esuka, it's not that of a young boy only defending a shop despite knowing nothing about how to run it, instead Shinemon defeats Esuka as a person who sees many possibilities laid out for his future. As such his imagination is not only stronger, but not limited to a narrow mindset.
Business owner and Stealth Mentor Esuka uses a Great Nature deck, often themed around animal teachers. Great Nature's new gimmick also shows a side of business Esuka tries to overcome, sometimes you get lucky and sometimes things don't go your way, but you can't let that dwell on you if you want to be successful.
Tatsuya saying that Malkuth-melekh is the only unit that can resurrect others may seem odd considering the fact the entire Granblue clan focuses on resurrecting units, until you realize that they don't truly resurrect people, but rather raise them from the dead as undeads.
In gameplay terms, Order Cards are comparable to spell cards in other games. In context to Vanguard, Order Cards would be comparable to leaders issuing orders to their troops, which in this case would be the Vanguard. The grade limitations also mean that only someone of that rank can issue the order.
Grade 4 and 5 units go beyond the normal limitations of a unit where most units will only go up to Grade 3. In context, Grade 4 units are transcended beings like Novelle Vauge or any of Gear Chronicles' Grade 4 units who lead the way much like what Grade 3 Vanguards are. The Grade 5 Valkyrion has to have its own space as it's basically like a god, its power is so great, the Astral Plane has to be established in order to contain it, and it doesn't even last long considering it disappears at the end of turn.
The Bermuda Triangle Grade 4's operate a bit differently as it's context is based on idols. A grade 4 idol would be a legendary idol whose music would influence all generations much like classical music artists.
The Grade 4 of Pale Moon can be seen as the grand climax in a circus performance.
Despite Blaster Blade being overwhelmed against the Jammers, Emi and Shuka always summon him to start with. Much like how Aichi always rides Blaster Blade when he rides to grade 2, Emi might be unconsciously picking up this habit from Aichi.
As for why he gets overwhelmed so often, the Jammer of the week are Grade 3 units, who usually are stronger in terms of base power causing the Blaster Pair to counter with giving Blaster Blade support with a booster or their own Grade 3 unit.
It is also worth noting that most units tend to be defeated in one attack or get straight up overpowered which makes sense since neither the Jammer nor other units have anything to guard themselves with besides their normal Base Power and just like the game they either get retired or accumulate too much damage.
